We hope to completely purify the T4 regA protein (gpregA), which we believe to be a translational repressor responsible for shutting off the synthesis of a large number of specific T4 early proteins. We plan to study the binding of gpregA to various T4 mRNAs and to test its effect on in vitro translation, all in hopes of understanding the molecular mechanism of the regA function. We will also pursue in more detail the basis of the high-temperature deficiency in phage production by regA mutants; we have evidence that T4 morphogenesis is disturbed, probably indirectly through greater competition by early mRNA against late mRNA for ribosomes. As part of a more general study of translational control by T4, we hope to identify the genes that control two T4 proteins we have found tightly associated with ribosomes.